ANALYSIS OF NORMALIZED RADAR CROSS SECTION ( sigma o) SIGNATURE OF AMAZON RAIN FOREST USING SEASAT SCATTEROMETER DATA.

A detailed analysis of the normalized radar cross section sigma **o signature of the Amazon rain forest was conducted by using Seasat scatterometer data. Statistics of the measured sigma **o values were determined from multiple orbit passes for three local time periods. Plots of sigma **o against incidence angle as a function of beam and polarization show that less than 0. 3 dB relative bias exists between all beams over a range of incidence angle from 30 degree to 53 degree . The backscattered measurements analyzed show the Amazon rain forest to be relatively homogeneous, azimuthally isotropic and insensitive to polarization. The return from the rain forest target appears relatively consistent and stable, except for the small diurnal variation (0. 75 dB) that occurs at sunrise. Also, small instrument gain biases in some of the processing channels were detected. This led to the development of an improved sigma **o algorithm, which uses a more accurate method for estimating the system noise power.